As a method for manufacturing a photoreaction product sheet, such as an adhesive tape, the following method is known. That is, a substrate of, e.g., a filmshape, is coated to form a photoreactive composition layer of an appropriate thickness, and the thus-applied photoreactive composition layer is caused to react by means of light irradiation with a light irradiation apparatus, thereby forming a photoreaction product layer. In many cases, light irradiation apparatus of this type employs cylindrical light sources as light sources, which are, in many cases, arranged vertically with respect to a feed direction of a photoreaction product sheet, which is subjected to irradiation (hereinafter such a product sheet is referred to as a “subject”) (see, e.g., Reference 1).
However, the cylindrical light source radiates light by means of discharging of electrodes on two sides thereof. Accordingly, illuminance of light is likely to be uniform at the center of the cylinder. However, it is likely to be distributed more sparsely towards the electrodes on the respective ends. To this end, a technique of arranging the cylindrical light sources parallel with respect to a feed direction of a photoreaction product sheet, which is subjected to irradiation, has been disclosed (see, e.g., Reference 2).
[Reference 1] JP 2000-86984 A
[Reference 2] JP 07-275775 A
However, the illumination device employed in Reference 1 and Reference 2 is a general illumination device which has been used conventionally. FIG. 6 shows a schematic view of an example of such an illumination device. As shown in FIG. 6, a illumination device of a conventional, general light-gathering type comprises: a light source 22; and a curved mirror 20 comprising a curved surface 21 (i.e., light reflection surface) which has a shape of a portion of an elliptic curve having the first focal point F1 and a second focal point F2 on a reference axis of the curved surface, in a cross-sectional surface perpendicular to the axial direction of the light source. In which, the light source 22 is disposed on the first focal point F1. Light radiated from the light source 22 is focused on the second focal point F2. As a result, as shown in FIG. 7, illuminance distribution obtained therewith is such that illuminance is the highest at a portion directly under the reference axis. Even when a curved mirror of a parallel light type is employed, the tendency that the illuminance is high directly under the reference axis and falls steeply in its periphery is the same, and a range where uniform illuminance is obtained is extremely narrow. In the case of using such illuminating device, a molecular weight of a photoreaction product which determines the characteristics of the product is depend not on the light quantity but on the illuminance of light. Accordingly, the degree to which uniform illuminance can be maintained on an irradiation surface is a significant factor that determines the quality of the product. For this reason, also in a case where the illumination devices are arranged either perpendicular or parallel with respect to the feed direction of a subject as disclosed in Reference 1 and Reference 2, the illumination devices must be arranged with gaps as small as possible therebetween for forming uniform illuminance distribution on the surface of the subject. Consequently, a considerable number of illumination devices are used, whereby power consumption is increased, along with a quantity of heat from the illumination devices. In addition, many of the cylindrical light sources are of comparatively high-energy type, whose illuminance is higher than that required for photo-polymerization. Therefore, since light must be attenuated by use of a filter or the like, rendering the cylindrical light source extremely energy-inefficient.
The present invention has been conceived in view of the above circumstances, and aims at providing an illumination device which is capable of effectively irradiating a subject with light from a light source and irradiating a wide range with light of uniform illuminance distribution, and light irradiation apparatus using the same.